Servo regions for recording servo information and data regions for recording user data have heretofore been formed alternately in a disk-shaped recording medium employed in a disk unit, such as a magnetic disk unit or a magnet-optic disk device, along the direction of rotation of the disk-shaped recording medium. A sample servo system is known for generating a clock signal for obtaining timing in order to reproduce servo information or record and reproduce user data. This type of system generates a clock signal from a clock mark recorded in advance at a discrete position (e.g., servo region) on the disk-shaped recording medium by a magnetic means or a physical means. Further, a sector servo system for generating a clock signal from a data string itself is also known.
The prior art will hereinafter be described using a sample servo type magnetic disk unit as an example.
FIG. 11 shows one example of a magnetic disk employed in a sample servo type magnetic disk unit. The magnetic disk 201 has concentric or spiral tracks. Each of the tracks is uniformly divided into a plurality of segments (frames), e.g., 100 segments along the direction of rotation thereof. Further, the plurality of segments are respectively divided into servo regions (servo segments) for recording servo information and data regions (data segments) for recording user data.
The servo region comprises an address region, a fine region and a clock region. A clock mark 202 for generating a clock signal is radially and continuously recorded in the clock region. In a reproduce isolated or solitary waveform of the clock mark 202, for example, the time of presence of a peak indicates the supply of clock information synchronized with the rotation of the magnetic disk 201 to a data system and a servo system.
A fine pattern 204 is recorded in the fine region. In a magnetic head positioning servo, the fine pattern 204 is a pattern which is required by a tracking mode for accurately positioning a head to the center of a target track by the magnetic head positioning servo and indicates the position of the magnetic head relative to the track. The fine pattern 204 is composed of four magnetic patterns of A, B, X and Y.
An access pattern (track address code) 203 is recorded in the address region. The access pattern 203 is a pattern which is required in a track seek mode for shifting the magnetic head to the target track by the magnetic head positioning servo, encoding track addresses by, for example, gray codes, and changing them in length and layout so that they differ every track.
The clock mark 202 is synchronized by a clock generating circuit to be described later. However, the approximate position of presence of the clock mark 202 must be sought before the establishment of initial synchronization. As a synchronous auxiliary pattern, a unique pattern 205 is recorded in the address region in a predetermined cycle in place of the access pattern 203, e.g., at several tens of points per one track. The unique pattern 205 is composed of a plurality of lines (patterns) continuous in the radial direction. The unique pattern 205 can be easily detected even before the generation of the clock signal. For example, a violation code, which does not appear in an encoded data series, is normally used. Upon establishment of initial synchronization, the unique pattern 205 is first detected and a clock gate signal is thereafter generated after the elapse of a predetermined number of clocks, whereby the reproduce isolated waveform corresponding to the clock mark 202 is extracted.
In order to recognize the position of the magnetic disk 201 in its direction of rotation, a pattern 206, which is called a "home index pattern", is recorded in an address region as one per perimeter, as an alternative to the unique pattern 205. After the initial synchronization has been established by the unique pattern 205, the detection of the home index pattern 206 is kept in a waiting state until the magnetic disk 201 makes a round at worst, in order to recognize the position (corresponding to the position where the magnetic head is floating) of the magnetic disk 201 in its direction of rotation thereof. Afterwards, frame synchronization (segment synchronization) is established. Thus, the magnetic disk unit is finally shifted to a normal recordable and reproducible mode.
User data is recorded in the data region and reproduced therefrom in units of, for example 512 bytes called "sectors". Further, the user data corresponding to each sector is recorded, for example, with a sector ID (Sector Identification Code) or an ECC (Error Correction Code) added thereto. Definition information corresponding to a data sector, flag information indicative of a defective sector, ect. are recorded as sector IDs together with a CRC (Cyclic Error Detection Code). Each sector ID has skip information indicating that the sector cannot be used due to, for example, defects, as well as information such as a track number, a head number and a sector number (see FIG. 12).
Incidentally, the above-described segments and sectors are not in a one-to-one correspondence with one another. FIG. 13 shows an example of the correspondence of segments (frames) and sectors. In this example, a sector 0 extends over a frame 0 and a frame 1, whereas a sector 1 extends over the frame 1 and a frame 2. Recording and reproducing operations effected on each sector are carried out while repeating their stop or resumption so that the servo regions intruded or introduced into the sectors are masked. These operations are done by controlling a hard disk controller (HDC) or a recording and reproducing circuit system in accordance with a timing signal output from a timing generating circuit.
Now, a system for recording user data without adding sector IDs thereto has recently been proposed and realized. In this type of sector ID-less system, information for each sector ID is stored in a, for example, semiconductor memory without being stored on the magnetic disk 201. Thus, a few percentage of regions that must be originally ensured on the magnetic disk 201 as a sector ID region, can be applied for the recording of the user data.
FIG. 14 shows a conventional magnetic disk unit 210 of a sector ID-less system.
The magnetic disk unit 210 has a magnetic head 211 for recording data in, and reproducing it from, the magnetic disk 201. The magnetic head 211 is mounted to one end of an arm (not shown) held by a rotatable pivot. Avoice coil motor (VCM) 212 used as a drive motor is mounted to the other end of the arm.
Further, the magnetic disk unit 210 includes a hard disk controller (HDC) 213 having an interface function for interfacing to a host computer, a data write/read control function, a function for adding an error correction code to write data and effecting an error correction on read data, etc., and a microprocessor (MPU) 214 for controlling the operation of the entire unit.
Here, programs for operating the microprocessor 214 are stored in a ROM (Read Only Memory) 214M incorporated in the microprocessor 214. A conversion table for converting logical block numbers LBA (Logical Block Address), each given during a write or read command produced from the host computer, to their corresponding physical positions (head number, track number, frame number and sector number) of the magnetic disk 201, and a sector ID information table 215 which indicates information about sectors with sector numbers, are stored in a boot region of the magnetic disk or a memory such as an EEPROM. FIG. 15 shows one example of a conversion table and FIG. 16 illustrates one example of a sector ID information table (they refer to corresponding examples shown in FIG. 13).
The magnetic disk unit 210 has a buffer RAM (random access memory) 215 for temporarily storing write data transferred from the host computer and read data transferred to the host computer. Incidentally, a sector ID information table 215T is generated on the buffer RAM 215. This is copied from the boot region of the disk or the memory, such as the EEPROM, upon drive initialization.
The sector ID information table shown in FIG. 16 will now be described. A defect indicates that its corresponding sector cannot be used due to the defect. A count indicates the number of bytes up to the initiation of the servo region and shows the proceeding to a process for stopping the recording and reproduction of data after the elapse of the number of the bytes till the passage of the servo region. Incidentally, "0" shows that the servo region does not interrupt its sector.
The magnetic disk unit 210 includes a record data generating circuit 216 for effecting a digital modulating process and a write compensating process on write data read from the buffer RAM 215 upon writing and added with an error correction code by the hard disk controller 213 and thereby generating record data, and a recording amplifier 217 for obtaining a recording current signal corresponding to the record data generating circuit 216. Upon the write compensating process, a micro-correction in magnetization reversal timing at writing is effected on a peak shift of a read signal due to magnetization reversal interference produced upon high-density recording.
The magnetic disk unit 210 has a reproducing amplifier 218 for amplifying a signal reproduced from the magnetic disk 201 by the magnetic head 211 upon reading, and a selector switch 219 for supplying the recording current signal output from the recording amplifier 217 to the magnetic head 211 upon recording and for supplying the signal reproduced from the magnetic disk 201 by the magnetic head 211 upon reproduction. In this case, a fixed terminal on the W side of the selector switch 219 is electrically connected to the output side of the recording amplifier 217. A fixed terminal on the R side of the selector switch 219 is electrically connected to the input side of the reproducing amplifier 218 and a movable terminal of the selector switch 219 is electrically connected to the magnetic head 211.
The magnetic disk unit 210 includes a data demodulator circuit 220 for detecting a waveform peak from a signal output from the reproducing amplifier 218 and effecting a digital demodulating process on the detected pulse, to thereby obtain read data. The read data has been added with the error correction code and is stored in the buffer RAM 215 after having been subjected to the error correcting process by the hard disk controller 213.
The magnetic disk unit 210 has a clock generating circuit 221 for detecting a reproduced signal corresponding to a clock mark from the signal output from the reproducing amplifier 218 and for generating a clock signal synchronized with the rotation of the magnetic disk 201 based on the detected signal, and a servo information detector 222 for detection of servo information from the output signal of the reproducing amplifier 218.
The servo information detector 222 comprises a detection portion for detecting a home index pattern from the reproduced signal and outputting a signal indicative of the position of origin of the magnetic disk 201, a detection portion for detecting a unique pattern from the reproduced signal upon initial synchronization and outputting a clock gate signal after the elapse of a predetermined number of clocks, a detection portion for detecting an access pattern from the reproduced signal and effecting a demodulating process on it to obtain track address information, and a detection portion for detecting a fine pattern from the reproduced signal and performing signal processing on it to obtain tracking information.
The clock generating circuit 221 is supplied with the clock gate signal from the servo information detector 222. Further, the clock generating circuit 221 extracts a reproduce isolated waveform corresponding to a clock mark in accordance with the clock gate signal, and generates a clock signal synchronized with the rotation of the magnetic disk 201 based on the reproduce isolated waveform. Incidentally, the clock signal generated from the clock generating circuit 221 is supplied to the servo information detector 222. Further, the clock signal generated from the clock generating circuit 221 is supplied to the aforementioned hard disk controller 213, record data generating circuit 216 and data demodulator circuit 220 and is also supplied to other necessary points.
The magnetic disk unit 210 has a position control circuit 223 for controlling the voice coil motor 212 in order to position the magnetic head 211 to a target track on the magnetic disk 201. The position control circuit 223 controls the voice coil motor 212 based on the track address information and tracking information output from the servo information detector 222. Incidentally, the position control circuit 223 is supplied with information about a target track address from the microprocessor 214 upon writing and reading user data, as will be described later.
Further, the magnetic disk unit 210 has a timing generating circuit 224 for generating timing signals indicative of positions of various information points on-the magnetic disk 201. A signal indicative of the origin position is supplied from the servo information detector 222 to the timing generating circuit 224 as a reset signal. Further, the timing generating circuit 224 is supplied with the clock signal from the clock generating circuit 221. The timing generating circuit 224 counts the number of clocks from the position of the origin and generates various timing signals, based on its count value.
The timing signals may include, for example, a servo gate signal and a data gate signal necessary for a recording and reproducing circuit system, a signal indicative of the origin position of the magnetic disk 201 necessary for the hard disk controller 213, a frame pulse indicative of a frame start position, a byte pulse indicative of a byte start position, a sector pulse indicative of a sector start position, and a switching control signal for the selector switch 219.
FIG. 17 illustrates an example of a configuration of the hard disk controller 213.
The hard disk controller 213 has an I/O interface 231 for interfacing to the host computer, a buffer controller 232 for controlling the writing of data in, and reading of it from, the buffer RAM 215, a disk sequencer 233 for sequentially controlling the writing of user data in, and reading of it from, the magnetic disk 201, and a control register 234 for holding or retaining data values necessary for the sequential control of the disk sequencer 233.
The control register 234 has the function of counting the number of frames from the origin position and the function of counting the number of bytes from the sector start position. The I/O interface 231, the buffer controller 232, the disk sequencer 233 and the control register 234 are electrically connected to the microprocessor 214 through a bus 235.
Further, the hard disk controller 213 includes a chip controller 236 for supplying the various timing signals supplied from the timing generating circuit 224 to the disk sequencer 233 and the control register 234, and for generating a record gate signal in accordance with instructions issued from the disk sequencer 233 upon write operation and supplying it to the timing generating circuit 224, and a clock controller 237 for supplying the clock signal supplied from the clock generating circuit 221 to respective portions.
Moreover, the hard disk controller 213 includes a serializer/deserializer 238 for converting write data (parallel data) read from the buffer RAM 215 into serial data upon writing, converting read data subjected to an error correction by an ECC circuit 239 to parallel data upon reading, and supplying it to the buffer RAM 215, and the ECC circuit 239 for adding an error correction code to data output from the serializer/deserializer 238 upon writing, for supplying the data to the record data generating circuit 216, and for effecting an error correcting process on data output from the data demodulator circuit 220 upon reading.
The operation of the magnetic disk unit 210 shown in FIG. 14 will be described next.
Immediately after the turning on of the power or after the occurrence of an out of synchronism state, an initial synchronism establishing operation is carried out. In this case, the selector switch 219 is electrically connected to the R side so that a signal reproduced from the magnetic disk 201 by the magnetic head 211 is supplied to the reproducing amplifier 218 through the R side of the selector switch 219. Further, the servo information detector 222 detects a unique pattern from the output signal of the reproducing amplifier 218. After the occurrence of a predetermined number of clocks, a clock gate signal is supplied to the clock generating circuit 221 from the servo information detector 222. The clock generating circuit 221 regards a solitary reproduce waveform developed within a clock gate signal producing period as a normal clock mark reproduce waveform, updates the phase of the PLL (Phase-Locked Loop) held thereinside, and synchronizes the phase of a clock signal with a clock mark.
After the establishment of the initial synchronization, write/read operations are performed. Prior to the write/read operations, a sector ID information table 215T (see FIG. 16) is generated on the buffer RAM 215 under the control of the microprocessor 214.
The write operation control of the microprocessor 214 is carried out in accordance with a flowchart shown in FIG. 18.
When a write command sent from the host computer is received in Step ST1, an LBA is converted to physical positions (head number, track number, frame number, sector number) of the magnetic disk 201, using a conversion table (see FIG. 15) stored in a semiconductor memory, such as a disk or an EEPROM, in Step ST2.
Next, in Step ST3, necessary values such as a start frame number, the present sector number (leading sector number in a start frame--1), a start sector number, an end sector number, etc. are set to the control register 234 of the hard disk controller 213.
When, for example, the write command is one for providing instructions for writing of 3 sectors from an LBA "00A1", the LBA is converted to the head number="0", track number="0010", frame number="0001" and sector number="0001" in Step ST2. In Step ST3, the start frame number="0001", present sector number="0000", start sector number="0001" and end sector number="0004" (because the sector 2 is represented as a defect) are set.
In Step ST4, the microprocessor 214 controls the selector switch 219 so that it is connected to the R side in association with the servo region and to the W side in association with the data region. A target track address (track number) is set to the position control circuit 223. Thereafter, the position control circuit 223 is caused to start a track seek operation. The track seek operation is done as follows:
That is, the position control circuit 223 compares a track address, based on track address information obtained by detecting an access pattern 203 with the servo information detector unit 222, with the target track address and controls the voice coil motor 212 so that the a track address at the present position coincides with the target track address. After the track address at the present position has coincided with the target track address, the position control circuit 223 controls the voice coil motor 212, based on tracking information obtained by detecting a fine pattern 204 with the servo information detector unit 222, so that the magnetic head 211 is positioned to the center of a target track. When the magnetic head 211 is positioned to the center of the target track, the track seek is completed.
It is next determined in Step ST5 whether or not the track seek operation has been completed. Even though not mentioned above, information about the completion of the track seek operation is supplied from the position control circuit 223 to the microprocessor 214. When the track seek operation is completed, the microprocessor 214 starts the disk sequencer 233 of the hard disk controller 213 in Step ST6.
The disk sequencer 233 is controlled by various timing signals supplied from the timing generating circuit 224. The disk sequencer 233 reads write data temporarily stored in the buffer RAM 215 in predetermined timing. The serializer/deserializer 238 converts the write data into serial data, which is added with an error correction code by the ECC circuit 239, followed by supplying it to the record data generating circuit 216.
In this case, the frame counter of the control register 234 is counted up in response to the frame pulse output from the timing generating circuit 224. The present sector number of the control register 234 is counted up in response to a sector pulse output from the timing generating circuit 224.
It is determined in Step ST7 whether or not the count value has coincided with the start frame number. If it is determined in Step ST7 that the count value has coincided with the start frame number, it is then determined in Step ST8 whether or not the present sector number has coincided with the start sector number. When it is determined in Step ST8 that the present sector number has matched with the start sector number, the routine procedure proceeds to Step ST9.
In Step ST9, the microprocessor 214 confirms the absence of a defective sector (defect=0), the storage of the write data in the buffer RAM 215, etc., by reference to the sector ID information table of the buffer RAM 215. After conditions are met, the microprocessor 214 reads the write data from the buffer RAM 215 and transfers it to the record data generating circuit 216 as described above. As a result, the recording of data is started.
It is next determined in Step ST10 whether or not one sector has been completed. When it is determined in Step ST10 that one sector has been completed, the routine procedure proceeds to Step ST11 where it is determined whether the present sector number coincides with the end sector number. If it is determined in Step ST11 that the present sector number does not coincide with the end sector number, then the start sector number is changed so as to correspond to the next sector in Step ST12. Thereafter, the routine procedure is returned to Step ST7 where the same control as described above is executed. On the other hand, when it is determined in Step ST11 that the present sector number coincides with the end sector number, then the write operation is completed.
It is understood from the sector ID information table shown in FIG. 16 that the servo region is intruded in a sector 1 after a "b" byte subsequent to its start. Even though not described above, the recording is stopped in the servo region, based on the count of a byte counter of the control register 234. The disk sequencer 233 can access this information in the sector ID information table 215T of the buffer RAM 215 for every sector. Thus, the write operation can be allowed to proceed according to this information.
It is understood from the sector ID information table shown in FIG. 16 that since a sector 2 indicates that the defect=1, it is a defective sector. In this case, the routine procedure bypasses Steps ST9 and ST10 and proceeds from Step ST8 to Step ST11.
Control on the read operation is performed in a manner similar to the control of the write operation described above. The disk sequencer 233 is started after the completion of track seek. Next, the start sector is accessed and the ECC circuit 239 performs an error correction process on read data output from the data demodulator circuit 220. Further, the so-processed read data is converted into parallel data by the serializer/deserializer 238, which in turn is supplied to the buffer RAM 215 where it is temporarily stored. Thereafter, the data is transferred to the host computer through the I/O interface 231. Incidentally, the selector switch 219 is electrically connected to the R side upon reading.
The aforementioned conventional magnetic disk unit 210 has the following problems:
(a) In the conventional synchronization establishment routine, a magnetic disk unit that has proceeded to the normal recordable and reproducible mode after the detection of the home index pattern 206 is kept in a waiting state, in order to recognize the position of rotation of the magnetic disk, until the magnetic disk has made a round subsequent to the establishment of the initial synchronization by the unique pattern 205. This rotation waiting time presents a problem upon switching between the surfaces. That is, when the data is recorded on and reproduced from both surfaces, the transfer rate is greatly reduced as compared with the normal transfer rate.
In order to avoid this, the positions of rotation of both surfaces need an extremely high-accuracy alignment upon recording the home index patter 206 or stamping. Recording and reproducing heads for the respective surfaces are required to be created with high accuracy relative to each other. However, this results in a great load on the manufacturing process. Since the number of servo samples increases and the physical width between the servo regions is so reduced, particularly in the case of the sample servo system, margin is correspondingly reduced. Even if the transfer rate is sacrificed, the present unit has no choice but to reconfirm the rotational positions from the viewpoint of reliability.
(b) The sector ID-less system for improving the efficiency of data offers a problem in terms of the reliability of the data during data recording. That is, since the data recording is started from the reading of the sector ID added with the CRC (cyclic error detection code), which has been written on the disk by formatting, the probability that data will be written in an erroneous position, is extremely low.
However, the writing of data in the erroneous position is still carried out in the sector ID-less system in the event that the counter of the hard disk controller 213 slips due to the missing of the frame pulse or sector pulse supplied to the hard disk controller 213. Further, a method of instantaneously preventing its writing has not been proposed. If the above writing has occurred in a track containing data written in the past, then data up to the origin position, where the counter is normally reset, is overwritten on the track, thus resulting in the risk of its destruction.
Incidentally, these problems occur even in a sector servo system.
It is therefore an object of the present invention to provide a disk-shaped recording medium capable of improving the reliability of a sector ID-less system and achieving prompt establishment of frame synchronization, and a disk unit using the disk-shaped recording medium.